This invention relates to thermal insulating material and, in particular, to a highly efficient, lightweight, compact material based on mesh and plastic film.
One of the most efficient thermal insulation systems yet devised consists of many layers of metallized mylar film interleaved with netting and joined by thermal bonding along the edges or by rivets. The nettings serve as spacers between the film layers to keep them from touching, thus limiting heat transfer by conduction and providing space for reflection of heat. The metallized mylar reflects heat and limits heat transfer by radiation.
Apart from the relatively high technology "super-insulation" systems used in space vehicles and aircraft, thermal insulation materials based on plastic film have not been commercialized to any significant extent, even though relatively simple systems have been proposed. For example, U.S. Pat. No. 3,707,433 describes a material consisting of two layers of metallized polyethylene separated by a fiberglass scrim or a layer of plastic foam and bonded into a sandwich by adhesive or by the foam. The use of adhesive to join the layers involves problems in manufacture, notably in drying an adhesive trapped between vapor impermeable sheets. The system of that patent is generally unsuitable for high speed, low cost production for at least that reason. Moreover, the adhesive renders the product relatively rigid and, therefore, generally unsuitable for uses in which flexibility is needed, such as in clothing. It is suggested in the patent that breathability can be imparted to the material by needle punching a layer of fibers through it; in fact, the tight bundles of fibers passing through the holes significantly limit vapor transmission. The manufacturing and use problems associated with previously proposed insulating systems based on metallized films have made them uncompetitive thus far with other materials, particularly plastic foam.